Edsta spat



R. VARLEY.

X-RAY SYSTEM.

APPLICATION FILED MAR. 1a. 1915.

1 $09,494, Patented July 8, 1919.

Witnwow: W 7 Wm 71/ v W 2 UNITED STATES PATENT OFFICE.

VABLEY, OI BNGLEWOOD; NEW JERSEY.

x-mr sys'rmr,

To all whom it may concern.

Be it known that I' Rrcmno VARLEY, a citizen of the United States,residing at Englewood, in the county of Ber en and State of New J erseyhave inven certain new and useful Improvements in X-Ray Systems, ofwhich the following is a full, clear, and exact description. i

This invention relates to a system for producing currents of highfrequency, density and potential suitable for X-rays and analogouspurposes, the object bein the provision of apparatus by which an -raytube ma be excited by currents of com aratively hig density, at amaximum e ciency of conversion, with apparatus of low cost caable ofoperation either direct from existing service circuits or from analternator, a motor generator or other converting machine of small cost,size and output, and without the use of current rectifiers or othermoving parts of a complex nature and requiring appreciable power intheir operation.

The improved system comprises a transformer capable of producin in thesecondary circuit, currents of hig electro-motive force coincident withcomparatively high amperage, in combination with a source of alternatingcurrent and means whereby the half waves of one polarity only of thecurrent supplied will e effective in producing current in the secondaryof the transformer, to the end that only unidirectional currents willcharge the tube. The invention contemplates the use of a transformer inwhich the magnetic flux is normally largely sup ressed in that limb ofthe core upon whic the secondary is located while substantially all ofthe flux is periodically permitted to become suddenly active in thatlimb, at which periods the sudden surging of the restrained flux inducesan instantaneous extraordinary high electromotive force in the secondarycircuit capable of jumping a wide gap between the electrodes of thetube. Due to this comparatively high electromotive force I am able touse a secondary coil of comparatively few turns and low resistance w ichaffords a comparatively large number of milliamperes of current in thesecondary circuit and a discharge in the tube of correspondingly greaterdensity and power of fpenetration.

In the accompanying drawings,

Figure 1 is a diagrammatic view of en- Specification or letters Patent-Patented July 8, 1919.

Application fled larch 18, 1815. Serial No. 15,270.

:uits and apparatus embodying my invenion;

F g. 2 is a similar view of a modification .of the invention, and

of alternating current, which may be eithera motor'generator or arotaryconverter, in e ther case delivering current from the slip rings g, tothe primary circuit 1, 2 throu a pole changing switch 3. T is a transormer having a core t in the form of a substantially closed magneticcircuit. On one s1de or limb of this core is a coil 4, here- 1n aftercalled the primary coil, connected with the rimary circuit wires 1, 2,while upon anot er part or limb of the core is located a coil 5,hereinafter referred to asthe secondary coil, of a com aratively largernumber of turns and of fi ner wire than is 1n the prlmary coil, andconnected in circuit with the wires 6, 7 which are connected, or to beconnected, with the respective and proper terminals of an X-ray tube R.Upon the'same limb of the transformer core with the secondary, isanother winding 8 havin the function of a choke coil and referretohereinafter as the choke coil. The circuit of this coil is normallyclosed through a spring tongue 9 resting against a contact stop 10, theton e being mounted in a position to be struc and forced away from thecontact 10 by a cam disk 11 mounted upon or to be driven by, the shaftof the supply machine G, the contact at 10 being broken once during eachrotation of the cam.

Assuming that the generator G delivers a sine wave current such asplotted in Fig. 3, the primary coil- 4 will be correspondinglysymmetrically energized setting up a magnetic flux in the transformercore t. Choke coil 8 being normally shortwcircuited at 10 effectuallyacts as a'choke upon the travel of lines of force through that part ofthe core under the choke coil and secondary coil windings. Rotation ofthe cam 11 in synchronous relationship with the generator causes thesudden opening of the circuit of coil 8 at a suitable point in thecurrent wave. Opening of the circuit of coil 8,-as stated, causes adisruptive discharge of current of high voltage to take lace 1n thesecondary coil 5 in circuit with t e tube. When the circuit of coil 8 isopened a magnetic surge of great intensity and speed occurs through theentire core of the transformat. A high voltage is immediately built upin the secondary coil 5 sufficiently to instantly bridge or break downthe gap between the electrodes of the tube. However, the discharge thusformed is not merely instantaneous but continues as long as the circuitof coil 8 is open. Upon the establishment of the discharge current flowsin the secondary circuit an the am ere turns of the-secondary coil takethe p ace, in their effect, of the ampere turns of the coil 8. Thechoking effect is controlled by the are or discharge in the tube, whichassumes, by reason of its establishment in the circuit of coil 5, arheostatic function, for the voltage across the a itself is sustained bythe flux change w ic in turn, is controlled by the amperage of thedischarge across the gap in the tube. Therefore with a certain changingof flux in the core, pref-- d erably partial y sustained by the activesource, increase of gap resistance decreases the current flow across thegap, allowing increase of flux and so reciprocal increase of gapvoltage, thus tending to current maintenance and stability. The s stemtherefore operates to instantaneousl reak down the resistance of the gapin t e tube with a high voltage and a current of high milliamperes, ascompared with a Ruhmkorff coil of equal watt intake.

Preferably, the nerator G is one which delivers one comp ete waveconsisting of a positive and a negative impulse, at each rotation andthe interrupting cam is so placed upon the shaft of the generator orgeared thereto, that it will 0 en the contact at 10 during only one of te im ulses, say the positive, in each rotation an allow the contacts toremain closed during the other or negative impulse and the remainder ofthe rotation, as illustrated in Fig.3, where the full lines of the curveindicate approximately the periods during which contacts 10 are open andthe dotted lines the eriods during which they are closed. In this manneronly unidirectional currents are induced in the secondary circuit, whichis necessary for the production of the x rays and the use of currentrectifiers with their attendant complication and consumption of power iseliminated. And while only the current impulses of one polarity of thegenerator, are utilized, this is compensated for by the fact that thepeculiar method of transforming affords the greater electro-motiveforceand renders it possible to obtain a greater amperage with a givenresistance of secondary circuit.

It is obvious that a multipolar nerator or other source at G may be usedw ich will yield more than one impulse of a certain olarity at-eachrotation. For instance, a

our-pole machine would give two positive and two negative impulses. Insuch case the cam 11 preferabl would be provided with two projectionsiametrically opposite each other and adapted to open contact 10 duringeach positive or each ne ative wave, as the case may be. The poechanging switch 3 is to be used at starting in case the discharge in thetube does not happen to be in the right direction. The cam 11 is smalland light ahd entails little or no expenditure of power to operate it sothat the converting machine G will not be burdened by its presence onthe shaft.

Instead of the mechanical circuit opener for the choke coil circuit, Imay, and in fact prefer to, use an electro-magnetic device and therebydispense with all rotating parts and the requirement of motor power atthe point where the tube is to be operated. Such a system is illustratedin Fig. 2 wherein P'inicates a polarized relay of which 12 is thevibrating armature located between poles 13, 13 on which are wounddifferentially the usual electro-magnetic coils. These coils have beenshown as permanently connected in series with the primary circuit of thetransformer, which circuit may be suplied from service mains 14, 1'5 andcontrol ed by manual switch 16. They may, however, be connected inparallel with said circuit. The armature of the relay is given a slightbias toward a contact stop 17 by a light spring 18 assisting the normalmagnetic bias. The normal polarity of the coils 13 and armature s is asindicated in Fig. 2. When there is a flow of current through the coils13 in one direction the normal polarity remains unchanged and thearmature s is drawn with a force, additional to that of the spring 18,against the contact stop 17. The opposite p ase. of the current willreverse the polarity of the coils 13, causing the armature to be movedto the left, away from the stop 17. Armature 12 and contact 17 are theterminals of the choke coil circuit so that the movements of thearmature 12 due to alternations in the primary circuit serve to open andclose the circuit of the choke coil and perform the same functions asthe cam 11 and spring blade 9 in the system of Fig. 1. The tension ofspring 18 is such as to insure the rompt closure of the choke circuitimmediately before the point of zero potential in the wave is reached.

The opening of the choke circuit at 17 is delayed slightly but notmaterially by this spring but such delay is advantageous in a sense,making the surge of lines more pronounced when the choke circuit isopened nearer the peak of the wave. The exact points in the half wave ofopening and closing the choke circuit may be adjusted in any convenientway, as by regulating the tension of the spring in the system of Fig. 2,while in Fig. 1 different lengths of cam on disk 11 can be used. Whensudden and excessive wide gap, the opening may occur later or nearer thepeak of the wave and when longer duration of the discharge is requiredthe opening may occur earlier. An average serviceable location andduration for the in Fig. 3. Under some conditions of structure andoperation, objectionable arcing may occur at the contacts which controlthe choke coil circuit, in which case it may be found desirable toconnect a condenser 19 across the contacts 10 in Fig. 1 or 19 in Fig.2'. Other plans for suppressing the arc may also be adopted, such asmaintaining the relay in a sealed chamber containing air or gas underpressure, or a non-oxidizing gas which will prevent destruction of thecontacts.

With the apparatus herein described X ray operations can be performedwith the greatest convenience. This is especially true with the systemwhich comprises the polarrectifiers and all rotating parts which add tothe complexity and expense of other systerms. 1 it may be remarked thatWhile the cam disk 11 is a light and simple piece of apparatus requiringalmost negligible power to drive it, nevertheless it may be dispensedopening period is indicated by the full lines Y with and a polarizedrelay inserted in the primary circuit 1, 2 and thus relieve themechanical generator of such slight load as the disk entails.

I claim:

1. In an electric system, the combination of a source of alternatingcurrent, a transformer supplied thereby, a choke coil associated withthe core of the transformer, and an electro-magnetic device actuated bythe primary current of thetransformer and controlling thecircuit of thechoke coil.

In connection with the system of Fig.

'2. In an electric system, the combination of a source of alternatingcurrent, a transformer supplied thereby, a choke coil associated withthe core of the transformer and a polarized relay in the primary circuitof the transformer and controlling the circuit of the choke coil.

In Witness whereof I subscribe my signa ture, in the presence of twowltnesses.

RICHARD VARLEY.

Witnesses WALDO M. CHAPIN, JosnPH A. BUoKLnY.

